This invention relates generally to gas turbine engines and, more particularly, to methods and apparatus for injecting water into gas turbine engines.
Gas turbine engines typically include a compressor assembly for compressing a working fluid, such as air. The compressed air is injected into a combustor which heats the fluid causing it to expand. The expanded fluid is then forced through a turbine.
The output of known gas turbine engines may be limited by an operating temperature of the working fluid at the output of the compressor assembly. At least some known turbine engines include compressor cooling devices, such as intercoolers, to extract heat from the compressed air to reduce the operating temperature of the flow exiting the compressor. As a result of the decreased temperatures, increased power output may be achieved by increasing flow through the compressor assembly.
To facilitate additional cooling, at least some known gas turbine engines include water injection systems that overcome some of the shortcomings associated with intercoolers. Such systems use a plurality of nozzles to inject water into the flow during engine operation. Each nozzle includes an air circuit and a water circuit which extend through the nozzle. Air and water flowing through each respective circuit is mixed prior to being discharged from the nozzle through a convergent nozzle tip. The air circuit includes a swirler located a distance upstream from the nozzle tip that induces swirling to aid the mixing between the water and the air.
The air exiting the swirler flows a distance downstream before being channeled radially inward within the convergent nozzle tip. As a result, a low pressure, high swirl region is created downstream from the swirler which may trap particulate matter suspended in the air in a continuous swirling vortex. Over time, continued exposure to the swirling particulate matter may cause abrasive erosion to occur within the nozzle tip. Furthermore, any water droplets trapped within the air circuit as a result of condensate from the air system or water drawn into the air circuit from the water circuit, may increase the severity of erosion that occurs.
In an exemplary embodiment, a nozzle for a gas turbine engine includes an air circuit and a water circuit that facilitate reducing erosion within the nozzle. The nozzle air circuit is formed by a first conduit extending along the nozzle. The nozzle water circuit is formed by a second conduit also extending along the nozzle and radially inward from the first conduit. Each circuit is in flow communication with a discharge opening. An air swirler adjacent the discharge opening discharges air towards and into water spray exiting the water circuit. The air swirler induces swirling into air flowing through the air circuit.
During operation, air flows through the air circuit and water flows through the water circuit. Air discharged from the air circuit is swirled with the swirler and impacts water discharged from the water circuit. More specifically, the air helps to atomize the water within the nozzle. The atomized water evaporatively cools a compressor flowpath for engine power augmentation. In one embodiment, the array of droplets evaporate within the engine to facilitate reducing operating temperatures and increasing engine peak power output. Furthermore, because the swirler is adjacent the nozzle discharge opening, swirling airflow immediately impacts the water after being discharged from the swirler. As a result, the swirler facilitates eliminating dwelling of water droplets or particulate matter within the nozzle.